Method of preparing arsenic compounds



Patented July 25, 1 950 METHOD. OF PREPARING ARSENIC COMPOUNDS Benjamin F. Tullar, Grosse Pointe Woods, Mich.,

assignor to Parke, Davis & Company, Detroit, Mich., a corporation of Michigan e No Drawing. Application January 31,1944,

Serial No. 520,552 4 Claims. (61.260440), 1 f

The invention relates to new and improved salts derived from 3-amino-4-hydroxyphenylarsenoxide.

The known 3-amino-4-hydroxyphenylarsenoxide compounds and their salts are extremely sensitive chemicals which tend to be rendered more unstable by contact with heat, moisture and air or oxygen,.or by exposure to light or by combinations of these circumstances. They are also subject to serious alteration upon storage whenever contaminated by, or combined with, small amounts of foreign .chemicals or solvents which may have been used in their preparation. It is thought that the great ellectiveness of 3 amino 4 hydroxyphenylarsenoxide and its salts in treating syphilis and for other therapeutic purposes is related in some way to this inherent sensitivity and chemical reactivity. Experience has shown that there are numerous difiiculties in the way of making even the slightest improvement in chemical stability of salts of this particular arsenoxide without at the same time decreasing the therapeutic effectiveness of such compounds.

A product intended for intravenous administration must be stable under the conditions that prevail from the time of ampouling the product until it is actually injected. Moreover, it must be a clear and particle-free solution or else a solid which will dissolve in a reasonable length of time, say 3 minutes, to form such a solution upon the addition of a suitable sterile solvent. The hydrochloride of 3-amino-4-hydroxyphenylarsenoidde obtainable on the market at the present time is prepared'by precipitation by means of organic solvents. Such hydrochloride dissolves quickly enough in aqueous solvent, but is too sensitive to heat, even when dry, to constitute a safe, effective and reliable product for storage and use in tropical climates. The apparent reason for this is, that the solvents used for dissolving the amine each manufactured lot of this dry organic 'solvent-precipitated hydrochloride and its mixtures with neutralizing agents so thatfit is sufiiciently stable even for use in temperate climates. Al-

though it is possible to produce satisfactory com'-' mercial lots for use in temperate climates; the

skill and care necessary to provide a safe and effective product by the known methods is such that the final product must be marketed at a relatively high cost per gram.

An object of this invention is to provide newderivatives of 3-amino-4-hydroxyphenylarsenoxide, and also dry mixtures of the same with neutralizing agents, which constitute products that are stable and effective for therapeutic purposes in tropical climates and under conditions where relatively high temperatures and strong 1 sunlight are encountered. A further object is to' provide such derivatives and mixtures which can be made by methods which will insure uniformity;

of product at a minimum cost of production.

A further object is to provide new compositions, that are stable and effective under the various.

conditions which may prevail fromthetime of.'.

their ampouling until they are applied to, or'

injected into, the patient by the physician and.

th hydrochloride of 3-amino-4-hydroxyphenylarsenoxide from aqueous solution and in the,

absence of organic solvents in order to avoid the above mentioned unfavorable effects of the organic solvents. I was able to prepare the. hydrochloride of 3-amino-4r-hydroxyphenylarsenoxide by dissolving the crystallinefree base hydrate, which is described in United States Patent No. 2,221,817, in one equivalentof aqueous hydrochloric acid of such strength that a 40+50%..

solution of the arsenical was obtained, cooling 1 the solution to about 0 C. and allowing it to stand.

at that temperature with occasional scratching to bring about crystallization, and then filteringand drying the crystallizing material in vacuo.

The product thereby obtained analyzes properly (CeHvOzNAsCl) for pure anhydrous hydrochloride 0f 3-amino-4-hydroxyphenylarsenoxide. However, it exhibits a peculiar undesirable slow solubility, either alone or mixed with alkaline or basic neutralizing compound, such as alkali carbonate or hydroxide. As much as 1530 minutes is required for the milky suspension, which first forms upon adding water to this particular hydrochloride, to change into a clear solution.

This crystalline anhydrous hydrochloride is therefore unsuitable for practical therapeutic use, mainly because of its delayed solubility. In view of its properties, it seems likely that this 'commund can be represented by Formula A in the following equilibrium and will not dissolve until it is slowly converted to its hydrated form, B.

(A) (13)., I In the above mentioned pneparatiomofsmfrbml Patent No. 2,221,817, the hydrochlorideproduct,

A. crystallizes only very slowly, even at"C'. 'lfhe f free base starting material from United States Patent No. 2,221,817 is a hydrated arsenicalnf formula, C,

Impreparing theAmsati'sfactory and slowly som ble' compound; A,-'- from the hydrated free hase C-'.as- -described-above, it a-ppears" that the hydrochloridaoid reacts with C" to give 13' andnthe slow rate ofcrystallization -of A=is due tw th'e time v l h'ydrous-product'is obtained which -is-ra-pidlysol 50 uble in water and farmore stable under-cone ditio'ns of use than the known product obtainede by-precipitation bymeansof organie -solventse- My j new "hydrochlorideis entirely free from organic" solvents andis much -more stable than the known hydrochloride obtaineob by usingon ganie solvents'.- lt als'o adistinctly -difierent chemicalcompound-from the slowiy-soluble *defi nitely crystaIline hydrochloride: A; since it readily soluble -inorganic" soiv'entssuch= as absolu-teethyl alcohol; dioxane, ethylene glycolmonoethyl ether ('cellosolvei) acetone, etc. whereas A'is insolubledn=these solvents'z It apei1 pears that mynew hydrochloride and i analogous salts ofother acids can be represented =b'ythe 6 general formula; v l

where A is the anion of a. suitable organic or inorganic acid. For example, the sulfate and citrate salts have the formulas.

. f'Iiheffollowine examples illustrate the preparation of my new hydrochloride, as well as preparation ofanalogoussalts'of acids other than hydrothe crystalline free base hydrate of United stamens i whim-111i Wthm the the iziventiiiint Example 7 2117 grams of crystalline s-aminol-hydroxyphenylarsenoxide, prepared as described in 20 United States Patent No.32,221,817, is dissolved in fifiieccrzpzfiiidilute hydrochloric; acidssolutionspreparedibyaaddinggbwater $0.816 icc-luof a36-%,-hydro.-.; ohloric acid until a volume of cc. is obtained-. Thislsolutionzof the, oxide-hydrochloride: is frozen a insasthinz-layer. coveringzztheslarge (inner surface: 1. ofsaacontainer andithe container;.then'tconnected:.

toaamhigh vacuum'auntilathersolid hydrochlorider appearsntoiithe geyezcto. beacompletelyrg, dry; The :1

laststnaces ofamoistureiarethemdriven :oif-of. the 12 valcuumzwh'ileiallowinggthe container; .to warm up:

tot. room temperature. a The): vacuum; is. then;

is fille d into s t enila: ambouls fnnder anhydrous conditions and sealed. The product -thusoob tained -is staple eyen; in-tropioab countries, for

mam;- n onths-andi ready forruse. The contents 5 of; .anta np ouleof; this-product -will instantly and..-

om le elmd clv fls wei s es t be r d i o m ed e r et v water ,to the'i extent of at.-least.-50%;

In g the same .mannern as described above-;- for theqrhydrochloride z other salts mare preparedwbysupstitn tinge equivalent. quantities: of; other suitganic acids of; this lgind .yieldingsaltswhich when 5 driede-fron atti e frozen state .are immediately .sol-= eet mhenfi s a .7. I

What,.- ,I as my invention is: 1 .-l Method-domobtainingi anstable; dry, -addition-2 0,- sa.lt\ of-;anac;id: of formula.:I-IA withc3-amino-4w 'ubletin waternt give a solution rhaving garpH not;-

hydroxyphenylarsen: an hydro) oxide. which comnrisesf reezing an (aqueous solution.-of.said

salt-and colnnletelyssublim in awaytthelioe there-l from ,u

The; hydrooh-loi ide .otsthislexample issoluble sini V r uurn A of saidformula represent-e ;k nsit elammw -anew-tox c idsi nousm 5 that aqueous solutions of said addition salt have UNITED STATES PATENTS a pH not greater than about pH 3.

2. Method according to claim 1 wherein the fgxg 81934 acid HA iS a. non-toxic mineral acid. 2 0 302 Reichel 2 935 3. Method according to claim 1 wherein the 5 2,092,036 Tatum Sept 7 1937 acid HA is a hydrohalic acid- 2,099,659 Reichel Nov, 16,1937 4. Method according to claim 1 wherem the 2,149,304 Masucci Man 7, 1939 acid HA is hydrochlmic 9015- 2,221,817 Scott Nov 19, 1940 BENJAMIN TULLAR- 2,222,333 Tullar Nov. 19, 1949 2,349,729 Hopkinson May 23, 1944 REFERENCES CITED FOREIGN PATENTS The following references are of record in the Number Country Date file this Fallen 260,382 Great Britain May 31, 1926 

1. METHOD FOR OBTAINING A STABLE, DRY ADDITION SALT OF AN ACID OF FORMULA HA WITH 3-AMINO-4HYDROXYPHENYLARSEN - (ANHYDRO) - OXIDE WHICH COMPRISES FREEZING AN AQUEOUS SOLUTION OF SAID SALT AND COMPLETELY SUBLIMING AWAY THE ICE THEREFROM UNDER VACUUM, A OF SAID FORMULA REPRESENTING THE ANION OF A NON-TOXIC ACID STRONG ENOUGH THAT AQUEOUS SOLUTIONS OF SAID ADDITION SALT HAVE A PH NOT GREATER THAN ABOUT PH
 3. 